GEANT4 Target Simulations for Low Energy Medical Applications

The GEANT4 code offers an extensive set of hadronic models for various projectiles and energy ranges. These models include theoretical, parameterized and, for low energy neutrons, data driven models. Theoretical or semi-empirical models sometimes cannot reproduce experimental data at low energies(<100MeV), especially for low Z elements, and therefore recent GEANT4 developments included a new particle\hp package which uses evaluated nuclear databases for proton interactions below 200 MeV. These recent developments have been used to study target designs for low energy proton accelerators, as replacements of research reactors, for medical applications. Presented in this paper are results of benchmarking of these new models for a range of targets, from lithium neutron production targets to molybdenum isotope production targets, with experimental data. Also included is a discussion of the most promising target designs that have currently been studied

Target Optimisation Studies for Surface Muon Production

The current paper discusses possible designs for a stand alone muon target for MuSR studies of condensed matter science. Considering the ISIS 7 mm graphite target as a reference, Geant4 simulations have been performed in order to optimize the target parameters with respect to muon and pion yield. Previous studies suggested that the muon production can be optimized by using a thin graphite slab target with an incident proton energy significantly lower than initially considered. Surface muon production obtained by firing an 800 MeV proton beam energy onto the target is simulated and potential improvements to the target material, geometry and angle orientation with respect to the incoming proton beam as well as an estimated performance of the muon target are presented in this paper. Implications for the ISIS muon facility are also discussed. A comparison of the pion production cross section between experimental data and three theoretical models for the latest four Geant4 versions is also included in this paper

5MW Power Upgrade Studies of the ISIS TS1 Target

The increasing demand for neutron production at the ISIS neutron spallation source has motivated a study of an upgrade of the production target TS1. This study focuses on a 5 MW power upgrade and complete redesign of the ISIS TS1 spallation target, reflector and neutron moderators. The optimisation of the target-moderator arrangement was done in order to obtain the maximum neutron output per unit input power. In addition, at each step of this optimisation study, the heat load and thermal stresses were calculated to ensure the target can sustain the increase in the beam power

GEANT4 Studies of Magnets Activation in the HEBT Line for the European Spallation Source

The High Energy Beam Transport (HEBT) line for the European Spallation Source is designed to transport the beam from the underground linac to the target at the surface level while keeping the beam losses small and providing the requested beam footprint and profile on the target. This paper presents activation studies of the magnets in the HEBT line due to backscattered neutrons from the target and beam interactions inside the collimators producing unstable isotopes

Simulation of high order short range wakefields

We present a formalism for incorporating intra-bunch wake fields into particle-by-particle tracking codes, such as MERLIN and BDSIM. Higher order wake fields are in- corporated in a manner which is computationally efficient. Standard formulae for geometric, resistive and dielectric wake fields are included for various apertures, particularly those relevant for ILC collimators

Simulations of Muon production targets

We review the recent simulations of muon production targets using the GEANT4 framework. Options for modifying the ISIS target are considered, as well as a wider study considering different materials, geometries and incident beam energies

Neutron Shielding Optimization Studies

The IsoDAR sterile-neutrino search calls for a high neutron flux from a 60 MeV proton beam striking a beryllium target, that flood a sleeve of highly-enriched 7Li, the beta-decay of the resulting 8Li giving the desired neutrinos for the veryshort-baseline experiment. The target is placed very close to an existing large neutrino detector; all such existing or planned detectors are deep underground, in low-background environments. It is necessary to design a shielding enclosure to prevent neutrons from causing unacceptable activation of the environment. GEANT4 is being used to study neutron attenuation, and optimising the layers of shielding material to minimize thickness. Materials being studied include iron and two new types of concrete developed by Jefferson Laboratory, one very light with shredded plastic aggregate, the other with high quantities of boron. Initial studies indicate that a total shielding thickness of 1.5 meters produces the required attenuation factor, further studies may allow decrease in thickness. Minimising it will reduce the amount of cavity excavation needed to house the target system in confined underground spaces

GEANT4 Simulations of Proton-Induced Spallation for Applications in ADSR Systems

In order to assess the feasibility of spallation driven fission and transmutation, we have simulated proton induced neutron production using GEANT4, initially benchmarking our simulations against published experimental neutron spectra produced from a thick lead target bombarded with 0.5 and 1.5 GeV protons. The Bertini and INCL models available in GEANT4, coupled with the high precision (HP) neutron model, are found to adequately reproduce the published experimental data. Given the confidence in the GEANT4 simulations provided by this benchmarking, we have then proceeded to simulate neutron production as a function of target geometry and thence to some preliminary studies of neutron production in an ADSR with the geometry similar to that of the proposed Belgian MYRRHA project. This paper presents the results of our GEANT4 benchmarking and simulations